Induction seaming tapes, systems and methods

ABSTRACT

The present invention pertains to novel tapes, tools and seaming systems for creating seams of rolled goods, especially carpeting, using induction heating. The present invention also provides improved seaming tapes for use in resistive heating methods.

[0001] This application is based upon and claims priority from U.S.Provisional Patent Application No. 60/384,523. Holzer et. al. filed May30, 2002.

TECHNICAL FIELD

[0002] This invention relates to induction activated seaming tapes,induction seaming systems and methods of seaming using induction for usein association with the formation of bonded seams of “rolled goods”including textiles, fabrics, felt, carpeting, wall coverings, and thelike as well as rigid and semi-rigid goods including paperboard, highpressure laminates, and the like.

BACKGROUND OF THE INVENTION

[0003] It is well known to attach rolled goods and other rigid andsemi-rigid goods to an underlying surface or substrate through anynumber of traditional methods including mechanical fasteners such asnails, staples, screws, tacks and brads, and chemical fasteners such asadhesives and cements which cure by volatilization of solvents, heat orchemical reaction. Additionally, Remerowski et. al. (U.S. Pat. No.5,935,369) and Krzeszowski (U.S. Pat. No. 4,123,305) teach methods ofbonding rolled goods to a work surface through induction bonding.However, in many applications, especially carpet seaming, it isundesirable to effect a bond between the rolled good and the underlyingsubstrate or intermediate, in the case of a carpet and the intermediatecarpet padding, while creating a seam bond between opposing edges of therolled good or of adjacent pieces of a rolled good. While stitching ofseams is common for most rolled goods applications involving fabrics andtextiles, stitching is not always practical or possible, especially inapplications where the presence of a visible seam would be unsightly ason a large tapestry, canvas or the like.

[0004] In order to address concerns relative to seaming of rolled goodswithout stitching, a number of different technologies and methods havebeen devised. For example, simple heat activated tapes comprised of abacking and a layer of a hot melt adhesive on one or both sides of thebacking have been developed for butt end and overlap seaming,respectively, of generally thinner fabrics and textiles or overlapseaming of thicker fabrics and textiles. These tapes are activated inplace by passing a traditional consumer iron over the site of the seam.

[0005] The heat of the iron passes through the fabric or textile to theadhesive, melting the same and forming a bond once the heat source isremoved and the hot melt allowed to cool. However, care must be taken informing the seam so as to avoid scorching the fabric or even melting ofthe fabric (especially in the case of certain fabrics of low temperaturesynthetic polymers and elastomeric materials) with the hot iron as wellas leakage or squeeze-out of the adhesive from the edges of the tape.Furthermore, if adhesive leaks through the seam or bleeds through therolled good itself and comes in contact with the hot iron, noxious fumesmay arise and, more importantly, the iron may no longer be suitable forits traditional use of pressing or ironing articles of clothing and thelike.

[0006] The problems associated with the use of adhesive tapes arecompounded and magnified in the seaming, particularly butt end seaming,of heavy duty, thick fabrics as used for tapestries and curtains andespecially in the seaming of carpets. For convenience, the followingdiscussion will be directed to carpet seaming. Carpet seaming tapes aregenerally 3-6 inches in overall width and are comprised of aheat-activated adhesive coated in the central 2-5 inches of these tapes,preferably a hot melt adhesive, a reinforcing fabric, and a carrierpaper, oftentimes coated with a silicone release coating on thebackside. A general schematic of the traditional carpet seaming tape isshown in FIG. 1 where the tape 1 includes a paper backing 2, oftencreped and frequently coated with silicone release coating on thereverse side 4, a reinforcement strip or scrim 3 for strength and athermally activatable adhesive 5. Reinforcement strip 3 can be a knit orwoven material and may extend to the edge of the tape but is frequently½ to 1 inch narrower than the paper carrier leaving equal spacing oneach edge. The adhesive may be in the form of a layer or beads or acombination thereof, but, in any event, is placed a set distance fromthe edges of the tape to prevent the molten adhesive from flowing offthe tape and inadvertently bonding the carpet to the pad during theheating and subsequent pressing steps. If this should occur, thesilicone release coating on the underside of the tape ensures that thetape itself will not bond to the padding, although this will not preventthe back of the carpet adjacent to the tape from bonding to the pad.

[0007] This seaming method requires the operator to first place theseaming tape, adhesive side up, directly under the open seam defined bythe opposing edges of the carpeting. Once the carpet and tape areproperly aligned, the operator then lifts the carpet and inserts aspecialized heating iron, whose lower surface is elevated to asufficient temperature to activate or melt the adhesive, underneath thecarpet and in direct contact with the heat activated adhesive of theseaming tape. Once the underlying adhesive has been melted or reacted,the hot iron is advanced along the seam to heat the next section ofadhesive. Concurrently, the trailing edges of the carpet behind the ironare brought in contact with the molten adhesive, manipulated to mateopposing edges of the carpeting to match any designs that may beincorporated into the carpet, and then pressed into the molten adhesiveto ensure good surface contact and integration of the molten adhesiveinto the rough surface of the carpet backing. Thereafter, the adhesiveis allowed to cool to form the bonded seam. The desired outcome is aseam that is not distinguishable from the rest of the carpet when viewedfrom the top of the carpet after the carpet has been stretched onto atack strip or like device that holds the finished carpet in place.

[0008] Though the foregoing is the most commonly practiced method ofcarpet seaming, it is not without its disadvantages. One particulardisadvantage is the incidence of peaking of the carpet at the seam oncethe carpet is stretched. Numerous improvements to the carpet seamingtapes have been proposed for addressing this problem including the useof multiple tapes in a side-by-side relationship (Johnston et. al. U.S.Pat. No. 4,749,433), extra-wide tapes (Johnston et. al. U.S. Pat. No.4,919,743), and plastic or metallic reinforcing elements (Matthews U.S.Pat. No. 5,691,051 and U.S. Pat. No. 6,110,565 and Matthews et. al. U.S.Pat. No. 5,198,300). Others have proposed the use of an excess ofadhesive at the centerline of the tape. One way in which this has beenachieved is through the use of specialized irons that include channelsor channeling features on their lower surface which divert moltenadhesive so as to create a ridge of excess adhesive directly under theseam. While all of these provide some relief to the peaking problem,they do so at the expense of added costs in relation to the materialsand manufacturing of the tapes and/or tools.

[0009] While the modified irons would seem a most efficient means toensure additional adhesive at the seam, they are not without problemsand shortcomings. Most notably, if the adhesive is heated significantlyabove its melting point, its viscosity becomes so low that a substantialamount may flow away from the ridge region as the tool is advanced andbefore the applicator can properly align and place the carpet edges.Additionally, because the adhesive in the formed ridge area is exposedto the air for the longest period of time, cooling will result in somesolidification or viscosity build up in the adhesive in this area sothat even if the applicator can ensure that adhesive is present at theinterface of the abutting edges, surface wetting may not be sufficientto ensure a strong bond at the interface, i.e., by the time theapplicator is able to align and place the carpet edges in properposition and press the same into the adhesive, the adhesive may not beviscous enough to flow into the interface between the abutting edgesand/or to develop a sufficiently strong bond with the consequence thatwhen the carpet is stretched the abutting edges separate or open: muchlike a paper cut opens when one pulls the skin on opposite sides of thecut in opposite directions.

[0010] In addition to the foregoing problems, the hot iron method doesnot allow for ease of redoing a seam once formed. Should the applicatorfind the pattern is off or that a gap exists in the seam bond, he mustemploy extreme care in reopening the seam to the point of the problem.In this method, the only way to open the seam is to rip it apart andthen strip the tape from the back of the carpet. This process canseverely damage the carpet and the carpet backing. Similarly, thismethod and tool do not allow for simple repairs in the event one needsto replace a small section of carpeting, for example to repair acigarette burn, or to re-bond a small segment of the seam that hasopened due to traffic. In essence, one must open an area sufficientlylarge to enable the tool to be placed under the carpet and removed.Furthermore, the heat of the tool often causes a relaxation of the twistof the carpet pile resulting in a noticeable difference in the carpettexture at the seam.

[0011] Besides the aforementioned difficulties with the process, the hotiron method has a number of additional concerns as well, includinghealth and safety related concerns. For example, the hot iron generatesthe emission of strong, offensive fumes from the adhesive. Additionally,because the irons, during use, generate a build up of adhesive andadhesive residue on the underside of the iron, i.e., that side incontact with the adhesive, the operator must often raise the temperatureof the tool periodically during the seam forming operation in order toensure good melting/activation of the adhesive. This can even occurduring a single seam forming operation where it is not possible tointerrupt a seaming operation to remove and clean a tool withoutseriously risking problems. As noted above, such higher temperaturesresult in lower viscosities of the adhesives, increasing the likelihoodthat adhesive will leak beyond the tape edges and bond the carpet and/orthe tape to the underlying pad or flooring as well as through the tapebacking itself. Additionally, such hot irons can permanently distort thecarpet backing as well as the carpet structure itself as a result ofscorching or, in the case of polymer based materials, melting and/orrelaxation of the carpet fiber twist; cause severe burns in workers whoaccidentally touch or come in contact with the hot surface of the iron;cause the emission of noxious fumes as a result of the melting andscorching of the adhesive. Additionally, a build up of adhesive andadhesive residue on the iron interferes with the heat transfer from theiron to the adhesive, thus slowing down the overall seaming process andunduly extending the time needed to complete the job.

[0012] A number of alternative technologies have been developed in aneffort to address some of the problems with the traditional irons andseaming techniques. In particular, concerns relative to adhesive buildupon the iron and the concomitant need for higher temperatures for theiron, and the associated problems with such higher temperatures, areeliminated by seaming methods and devices wherein the heat needed foractivating or melting the adhesive is generated within the seaming tapeitself and no tools come in direct contact with the adhesive.Additionally, these alternative methods involve tools that do not becomeexcessively hot in use and, thus, concerns for burns to the applicatoror the carpet are not an issue. Further these alternative technologiesdo not involve the use of tools which travel beneath the carpet andabove the seam tape, thus making the seaming method much easier.

[0013] One of the alternative methods involves resistance heating as ameans of melting or activating the adhesive. For example, Brooks (U.S.Pat. No. 4,416,713), Middleton (GB 1,499,801) and Rodenbaugh (GB1,507,851) each teach methods of carpet seaming using electricallyconductive seaming tapes, i.e., seaming tapes similar to those used intraditional iron seaming methods except that they have an electricallyconductive resistance element incorporated into the tape. In practice,each end of the tape is connected to an electrical current supply sourceto create a circuit. Heat generated by resistance heating as the currentpasses through the conductive element then melts or activates theadhesive. This eliminates many of the problems with the hot iron methodand device but creates additional problems as mentioned below.

[0014] Because the tape is activated for the whole length of the seam atonce, special care must be taken to ensure that the whole seam isproperly aligned before inducing the current. Any movement of the carpetbefore the seam is cured or set, even as a result of a misstep by theapplicator at or near the seam, may throw the entire seam out ofalignment. Additionally, any break in the conductive element in the tapewill render the entire length of the conductive seaming tapeineffective. In this respect tears or breaks in the conductive materialmay occur during the manufacture of the tape, in the course of layingthe tape and carpet or as a result of forces pressing down on the tapeafter its placement, e.g., as a result of a misstep or the placement ofa heavy and/or sharp edged article on the seam. More importantly, thismethod requires costly, bulky and inconvenient current supply equipmentcapable of generating currents of over 100 amps in order to generatesufficient heat along a lengthy seam to sufficiently heat the adhesive.

[0015] To some extent the need for bulky and costly equipment may beaddressed by superimposing one strip of the conductive material overanother with an intervening electrically insulating material, isolatingthe one from the other, (Brooks U.S. Pat. No. 4,610,906) or by placingtwo narrow strips of conductive material in a spaced, side-by-siderelationship along the length of the seaming tape (Baxter AU57288/80).In use, a conductive bridge is applied linking each conductive strip tothe other at one end of the tape and the leads from the power source areattached to the conductive strips at the opposing end of the tape. Bothtapes present problems of manufacture and handling to ensure that theconductive strips do not touch each other. In the latter, the stripsmust be placed carefully to ensure they do not touch; whereas in theformer, care must be taken to ensure that nothing pierces the tape, ahappenstance that could create a short through the electricallyinsulating layer. Furthermore, because the heat generated by theconductive material is fairly constant along the conductive element andacross its width (assuming uniformity in the material), the use ofthicker regions of adhesive can create problems as the time to melt theadhesive in such regions is longer than in thinner regions. Thus, theadhesive in the thinner regions will achieve a lower viscosity and havea greater tendency to flow before the adhesive in the thicker regions issufficiently melted to effectively bond the carpet. This can lead toleakage of the adhesive from the seam.

[0016] A second alternative carpet seaming technology relies uponinduction heating and induction activatable seaming tapes. Inductionactivatable seaming tapes are similar, in many respects, to theresistance tapes except that heating results from eddy currents andhysteresis effects that are induced in a susceptor material, e.g., afoil layer or strip, upon being exposed to electromagnetic fields.Although Middleton (GB 1,499,801) primarily focused on resistance tapeswherein the conductive medium is a perforated conductive foil, Middletonalso indicates that these tapes may be activated by induction. Nakano(EP 0237657) also teaches carpet seaming using induction activatableadhesive tapes that are activatable upon exposure to alternatingmagnetic fields of high frequency. Finally, Sakai et. al. (JP 1200937and JP1203825) teach induction heating apparatus and induction carpetbonding methods wherein the induction tool for generating the highfrequency magnetic field has three circular coils in a linearrelationship corresponding, in use, to the centerline of the seamingtape. It is believed that this technology was commercialized byHiroshima in Japan; however, it has since been removed from the marketdue to poor performance and acceptance of the product.

[0017] While induction seaming methods as taught in the prior art willaddress many of the issues and detriments of the iron seaming method andthe resistance seaming method, they still have various shortcoming oftheir own. For example, leakage of activated or melted adhesive from theedge of the tape is still of concern, especially if the adhesive asapplied to the tape is close to the edge. More importantly, inductiontools and induction activatable tapes taught to date for use in carpetseaming suffer from poor heating in the area of the scam line orcenterline. With such tapes and tools, the prominent heating occurs atthe edge of the susceptor and not at the centerline of the susceptor.Indeed, the traditional induction tools taught in the aforementioned artprovide little, if any, heating at the centerline of the tape due to thefact that the induced electric field and heating is very weak directlyunder the center of the coil. Since the carpet seam itself overlies thecenterline of the tape, that area of the seam that most needs heat toensure a good bond receives the least amount of heat. Consequently,there can be unbonded gaps or weaknesses in the seam as a result ofincomplete or insufficient heating of the adhesive directly under theseam. Although activation of the induction tool for longer periods oftime may allow additional heat to traverse the tape to the centerline,in reality this is not likely to occur to any significant extent sincethe more ready direction of heat transfer is through the foil to theother layers of the tape and carpet rather than across the thin foil.Consequently, even if such transverse heating were possible, by the timesufficient heat transferred to the centerline area, the other componentsof the tape and carpeting in contact with those regions of the tapewhere heating was effected, particularly at or near the edges of thesusceptor, would suffer from excessive heating resulting in scorchingand burning of the adhesive, other tape components and/or the carpeting.These problems are even further magnified and compounded if the tapesemployed thicker adhesive regions in the centerline area.

[0018] Thus, there remains a need in the art to design heat activatabletapes that lessen or eliminate the concern for adhesive leakage orsqueeze-out, without increasing, or substantially increasing, the costsof the tape.

[0019] There also remains a need in the art to design tapes which arereadily activatable by induction and provide suitable, durable carpetseams and, in a preferred respect, have thick regions of adhesive in thecenterline to enhance butt end bonding and reduce the likelihood ofpeaking without being concerned that excessive induction times and heatwould be needed and without risking scorching or burning of the tape,the carpet backing or even the carpeting itself.

[0020] There also remains a need in the art to design induction seamingsystems whereby induction tools and tapes are specifically designed foruse in combination so as to provide enhanced performance, whether foraddressing adhesive leakage or squeeze-out, peaking or merely forimproving bonding in the centerline region of the tape withoutoverheating the edges of the tape.

SUMMARY OF THE INVENTION

[0021] In one aspect, the present invention provides novel seamingtapes, which may be activated by induction or resistance heating,wherein the incidence of adhesive leak or squeeze-out is greatly reducedif not eliminated. Such seaming tapes include isolated strips of a heatsink material, which may be of the same material as the conductive orsusceptor material, which run parallel to each edge of the tape andintermediate the edge of the tape and the susceptor or conductivematerial which tends to be centered on the tape. Although the strips ofthe heat sink material may be placed so as to leave a narrow borderalong the edge of the tape, much as current tapes leave a border tocatch squeeze-out adhesive, it is also contemplated that the outer edgesof the strips of heat sink material may be coterminous with the edges ofthe tape. This process results in the relocation of the traditionallyhottest part of the induction tape from the edge to a more inwardposition.

[0022] The present invention also pertains to improved seaming methodswhereby adhesive leakage or squeeze-out is significantly reduced oreliminated as a result of the use of the foregoing seaming tapes as wellas to carpet seaming systems comprising the aforementioned seaming tapesand induction tools designed to operate with said tapes.

[0023] In another aspect, the present invention provides novel inductionactivatable seaming tapes wherein the susceptor layer comprises twoelectrically isolated, parallel, co-planar susceptor elements that areseparated by a gap that essentially, and preferably, corresponds to thecenterline of the tape. In a preferred embodiment, the center region ofthe tape, including the aforementioned gap, is overlaid with a thickerbead or layer of adhesive, as compared to the average thickness of theadhesive across the width of the tape, so as to provide added adhesiveto ensure good bonding of the butt ends of the carpet at the seam.

[0024] The present invention also pertains to improved seaming methodswhereby gaps or weaknesses in the seam bond due to incomplete orinsufficient heating of the adhesive directly underlying the seam iseliminated as a result of the use of the foregoing seaming tapes as wellas to carpet seaming systems comprising the aforementioned seaming tapesand induction tools designed to operate with said tapes.

[0025] In another, yet related aspect of the present invention, thereare provided improved conventional induction activatable seaming tapes,without the novel gap mentioned above, wherein the improvement pertainsto the inclusion of regions of thicker adhesive in the centerline areaof the seaming tape and improved induction tools specially designed foruse with such tapes. In following, the present invention pertains to animproved method of carpet seaming using the improved tapes to reduce oreliminate peaking and a double racetrack coil induction tool wherein thecoils are side by side, relative to the centerline of the tape and thecorresponding axis of the induction tool coil, as compared to prior artmulti-coiled tools where the coils are arranged in a linear or in-linerelationship relative to the centerline of the tape and the axis of theinduction tool.

[0026] Finally, in another aspect of the present invention, there areprovided seaming tapes having the combined attributes of theabove-mentioned tape designs as well as improved methods of seamingusing such tapes as well as the seaming systems comprising such tapesand the inductions tools specialized to optimize the performance ofthose tapes.

[0027] The use of these inventions results in improved seam qualitywithout drastically altering the seaming process and, in some instances,reducing costs. Additionally, the seaming methods of the presentinvention do not produce a significant amount of heat in, on or belowthe carpet, particularly as compared to the traditional seaming ironmethod; have reduced odorous emissions overall; and allow for easybonding from the top of the carpet.

BRIEF DESCRIPTION OF THE DRAWINGS

[0028]FIG. 1 shows a schematic representation of a conventional carpetseaming tape used with a seaming iron.

[0029]FIG. 2 is a cross-sectional view of the base and electricallyactive layers of a seaming tape made in accordance with the presentinvention wherein dead zones are present at the edge of the tape.

[0030]FIG. 2a is a top view of the tape foundation of FIG. 2.

[0031]FIG. 3 is cross-sectional view of a completed seaming tape usingthe tape foundation of FIG. 2.

[0032]FIG. 4 is a depiction of the footprint of a double racetrack coil.

[0033]FIG. 5 is a cross-sectional view of the base and susceptor layerof a seaming tape made in accordance with the present invention whereina gap or slit exists down the centerline of the susceptor layer.

[0034]FIG. 5a is a top view of the tape foundation of FIG. 5.

[0035]FIG. 6 is a cross-sectional view of a completed seaming tape usingthe tape foundation of FIG. 5.

[0036]FIG. 7 is a graph showing the normalized power density acrossone-half of the width of the susceptor (from the centerline to the edge)for four different coil separations.

[0037]FIG. 8 is a graph showing a finite element analysis of thenormalized power density across one-half of the width of the susceptor(from the centerline to the edge) for three different susceptor widths.

DETAILED DESCRIPTION OF THE INVENTION

[0038] In the simplest of terms, the seaming tapes made in accordancewith the present invention comprise three key elements, a base layer,one or more susceptor or conductive layers and one or more adhesivelayers. For applications needing high strength, particularly transversestrength across the seam, the tape will also include one or morereinforcing layers. It is possible, of course that the reinforcement mayitself be integrated into or comprise the base layer. While these veryelements form the structure of conventional induction and resistanceseaming tapes, the tapes of the present invention differ markedly interms of the design and construction of the susceptor or conductivelayer and, insofar as they pertain to tapes suitable for inductionactivation, the design or configuration of the adhesive layer(s). Thetapes according to the present invention may be one-sided or if used toprepare an overlapping seam or to bond a butt end seam to a substrate,double-sided.

[0039] Generally speaking, the tapes have a length and width whichcharacterize the plane of the tape. The height or thickness of the tapeis determined by the number of layers making up the tape as well as thethickness of each layer. The overall length of the tape is irrelevantsince, typically, tape portions are cut from a spool of tape to fit thespecific application. The width of the tape is largely dependent uponthe application to which the tape is to be used. For example, forseaming light fabrics, it may be sufficient to employ a tape of about ½inch width or larger. On the other hand, tapes for heavy-dutyapplications, e.g., carpet seaming, will be on the order of three to sixinches or more. Generally, such tapes would not exceed eight or soinches as the costs associated with such widths make them prohibitivelyexpensive, not to mention the costs of constructing induction toolslarge enough to activate the tapes. Finally, the tape should be as thinas possible so as to avoid noticeable rises in the fabric, textile orcarpeting where the seam is formed as well as to retain flexibility inthe tape, especially so that it can be easily inserted into a cut in acarpet for easy repair and to enable sale in coiled form. The tapecenterline, as that term is used herein, is the midpoint of the tapeacross its width. In a seaming operation, the seam to be formed willgenerally line up directly above the centerline of the tape. In thisway, the surface area of the adhesive of the tape is equally apportionedto each end of the fabric, textile or carpeting to be bonded so as toachieve maximum strength and durability in the seam.

[0040] As noted above, the seaming tapes are built upon a base layer.Most commonly, this base layer is made of a paper, preferably flat,creped or extensible Kraft paper, or could be formed of any othermaterials, such as cloth, plastic film, or the like, which currently isused for many seaming tape constructions. The base layer itself may beof a laminate construction comprising multiple layers of the paper orthe like as well as incorporating a reinforcing material, e.g.,individual fibers (continuous or chopped), a woven or non-woven fabricor mesh, a screen or other mesh like material, made of natural orsynthetic materials including fiberglass, nylon or polyester. The baselayer is preferably flexible so as to maintain ease of use and to allowthe tape to be coiled.

[0041] The adhesive is typically a hot melt adhesive or a reactive hotmelt adhesive. Such hot melt adhesives are generally solvent-freeadhesives based upon a number of different chemistries including:ethylene vinyl acetate (EVA) copolymers, styrene-isoprene-styrene (SIS)copolymers, styrene-butadiene-styrene (SBS) copolymers; ethylene ethylacrylate copolymers (EEA); and thermoplastic and reactive polyurethanes.Different hot melt adhesives have different ranges of temperature overwhich they are activated; however, many are characteristically solid attemperatures below 180 degrees Fahrenheit (° F.) and low viscosityfluids above 180° F. that rapidly set upon cooling. Others havetransition temperatures as low as about 150° F.: of course the actualtransition temperature of a given hot melt adhesive depends upon thechemistry of that particular adhesive.

[0042] Generally speaking, the temperature activation range of a givenhot melt adhesive depends upon the ability of the adhesive to wet andflow onto the surface of the adherends under the pressure andtemperature conditions of application. This is dependant upon therheology of the adhesive, which is a function of the chemicalcomposition and molecular weight of its constituents. By selecting andevaluating adhesives that provide end-use performance as required by theapplication as well as those that have a broad activation range, one canoptimize the tape design to achieve the maximum bond area andperformance ensuring the greatest factor of safety when used.

[0043] Essentially any hot melt adhesive used or known for use in carpetseaming applications can be used in the present invention. Such are wellknown and widely available. The adhesive is present as a continuouslayer of even or varying thickness across the width of the susceptor, asa series of parallel beads and/or strips extending the length of thetape or as a combination of the two. Alternatively, the adhesive may bepresent as beads, films or adhesive strips in the centerline region ofthe tape, preferably the centerline and the susceptor edge region of thetape. In the induction activatable tapes, where the adhesive is notpresent in the susceptor edge region, it is important that the width ofthe susceptor be significantly wider, generally at least about 1.3times, preferably about 2 times, wider than the width of the coil toavoid excessive heating at the edge of the susceptor.

[0044] As noted, the adhesive may be of uniform or, preferably, varyingthickness, with a greater thickness being present in the centerlineregion. Adhesive profiles (i.e. cross-sectional views) of varyingthickness may be achieved by any number of methods, as known to thoseskilled in the art, including extruding a film or strip of adhesive ofthe desired profile, by building successive layers of the adhesive atspecific locations on a base layer of adhesive or by laying a film ofliquid adhesive and using one or more scraper tools having the desiredprofile on its lower edge. The specific thickness of the adhesive layerwill depend upon the intended end use application. Thin films, generallyfrom about 1 to 3 mils may be used for simple bonding of textiles andfabrics; whereas thicker adhesive layers, generally on the order ofabout 10 to 200 mils, preferably 20 to 140 mils, more preferably 40 to100 mils, will be needed for heavy duty fabrics, especially carpeting.As noted herein, thicker regions of adhesive may be desirable forcertain end-use applications. In the latter, it is desirable to ensurethe adhesive is of sufficient thickness so that it will penetrate intothe rough underside of the carpet backing and, most preferably, into thecarpet seam itself to enhance bonding of the butt ends of the carpeting.

[0045] Conductive materials and susceptors suitable for use in theconstruction of conductive tapes and induction activatable tapes,respectively, are well known. Indeed, for the most part, suitablesusceptors, as described below, are also suitable for use as theconductive material for resistance heating applications, and vice-versa.Clearly there are, however, some instances where the two classes do notoverlap. For example, extremely thin foils used for induction may not beable to carry the current without burning through the foil in resistanceapplication. The latter may require thicker foils. Similarly, a seriesof parallel wires or conductive strips of very small width will performwell for resistive applications but will not have sufficient surfacearea to couple to the coil to enable induction heating. For ease ofreference, the two are oftentimes herein referenced aselectro-responsive materials.

[0046] The width of the electro-responsive material is a matter of thewidth of the bond line to be formed as well as the method by which it isto be activated. For resistive heating and conductive elements, thewidth and/or number of conductive elements are gauged by the width ofthe bond line. On the other hand, for induction applications, the widthof the susceptor element or elements must be sufficient that theelectromagnetic field generated by the coil of the induction tool usedwill create eddy currents in the susceptor and that the eddy currentsgenerate sufficient heat, but not excessive heat, to melt the adhesiveto form a suitable bond. If the width of the susceptor is too small,there is insufficient width for the eddy currents to form. Even whereeddy currents are generated, the width must be sufficiently large toavoid excessive heating at the edges. Thus, proper susceptor width is amatter of coil design and size as well as the width of the bond area tobe formed.

[0047] Electro-responsive materials suitable for use in the constructionof the laminates of the present invention include essentially anystructural material capable of absorbing electromagnetic energy andconverting such energy to heat. For example, the electro-responsivematerial may be comprised of a carbon fabric, mesh screen or a metal ormetallized material selected from foils, sheets, fabrics and meshes orscreens. The foil or sheet may be continuous or solid across its surfaceor it may have random or patterned slits, punch-outs or cutouts. Metalsuseful in the preparation of the electro-responsive materials includecopper, steel, aluminum and other electrically conductive metals.Generally speaking, the electro-responsive material orelectro-responsive layer has a thickness of about 0.01-3 mils (0.00001inch-0.003 inch) or more, preferably 0.05-2 mils, or most preferably0.01-1 mils. In the case of eddy current induction, especially whenaluminum foil is used, the thickness of the susceptor layer may besomewhat less, from 0.01-2 mils, preferably 0.05-0.75 mils, and mostpreferably 0.08-0.55 mils. The specific selection of the susceptormaterial and form of the susceptor material is dependent, in part, uponthe type of electromagnetic energy to which the tape is exposed, e.g.,low frequency, medium frequency, and high frequency. For convenience,practicality, and safety, heating is preferably developed using low tomedium frequency electromagnetic waves (˜2 kHz to ˜1 MHz) by inducededdy currents alone or in combination with hysteresis heating. In thisrespect, it is preferred that the susceptor be in the form of a sheet,foil, or mesh, which may be perforated, non-perforated, or patterned,with or without a constant thickness, and made of aluminum.

[0048] Additionally, the seaming tapes of the present invention mayinclude a reinforcing layer comprising individual fibers (continuous orchopped), a woven or non-woven fabric, webbing or mesh, or otherwebbing, mesh or screen like material, made of natural or syntheticmaterials including fiberglass, nylon or polyester. This reinforcinglayer is sewn or bonded into the tape construction to provide lateralstrength across the seam.

[0049] While many of the materials from which the tapes of the presentinvention are conventional for conductive and induction activatableseaming tapes, it is the novel orientation and configuration of theseelements as taught by the present invention which provide unique andmarkedly improved seaming tapes, and resultant seams, overcoming many ofthe short falls of the state of the art resistance and induction seamingtapes. For convenience, the following discussion will be specific tocarpet seaming tapes, methods and systems; however, those skilled in theart will readily be able to modify the teachings and principles setforth herein to use the same for seaming most any kind of “rolledgoods”, including textiles, fabrics, felt, carpeting, wall coverings,and the like, as well as rigid and semi-rigid goods includingpaperboard, high pressure laminates, and the like. It is understood thatthe term “rolled goods” is used herein to refer to a general category ofgoods and is not to be literally construed. While most roll goods aresold in bulk in a roll form, the present invention clearly applies togoods of the type described that are in sheet form as well.

[0050] Carpet seaming requires the creation of a band of bond area alongthe seam line of two pieces of carpet that are being joined. The bondmust be essentially continuous along the length of the seam and must besomewhere between about ½ inch and about 4 inches wide. Additional bondareas may be present, for example, there may be a separate bond linealong or near the edge of the tape; however, the key bond area is thebond in the centerline area of the tape. Gaps or weak spots in the bond,of significant size, will open up when the seam is stretched and beunsightly in the finished seam as well as result in a seam of poor orlow durability. The preferred centerline bond width is between about 1inch and about 3 inches, most preferably about 2 inches in width. Thiswidth provides a good trade between strength (wider is stronger and moredurable under foot traffic) and cost (wider uses more adhesive and istherefore more expensive).

[0051] According to a first embodiment of the present invention, seamingtapes that exhibit a markedly lessened tendency to experience edge leakor squeeze-out of adhesive or that are free of edge leak or squeeze-outcan be produced by creating “dead” zones in the susceptor material orintroducing a co-planar strip of a damming material between thesusceptor material and the edge of the tape, preferably along the edgeof the tape. As shown in FIGS. 2 and 2a, the foundation 10 of a seamingtape according to this embodiment of the present invention comprises abase layer 11, generally a strip of Kraft paper, and a susceptor layer12. The susceptor layer 12 comprises the susceptor element 14 andisolated edge strips 13 isolated by slits 17. The edge strips may be ofthe same material as the susceptor element or a different material solong as they do not generate or conduct sufficient heat to melt theadhesive when placed in the electromagnetic field. However, it is notedthat the material comprising the dam or edge strips, as they areinterchangeably referred to in this application, may, in fact, be a heatsink material, i.e., a material that readily absorbs heat from othermaterials in which it is in contact, so long as it does not conductenough heat to enable or facilitate the flow of adhesive past the dam tothe edge of the tape. Suitable damming materials include hightemperature polymers and plastics, preferably elastomeric or flexible innature, paper or paper-like materials, as well as metal foils,regardless of whether the metal is electrically conducting ornon-conducting. As shown in FIG. 3, the seaming tape is completed by thesubsequent addition of one or more adhesive layers 15 and, optionally, areinforcing layer 16, which may be directly adhered to the susceptorlayer or applied to an intervening adhesive layer 15 a. The uppermost ortop layer of the construction is an adhesive layer.

[0052] The width of the edge strips is generally less than ½ inch,preferably less than ¼ inch. In any event, the width of the edge strip13 is such that eddy currents and/or hysteresis heating cannot beachieved in the edge strip sufficient to melt the adhesive when aninduction tool, otherwise capable of activating the seaming tape, iscentered over the seaming tape and activated. This is generally seenwhen the width of the edge strips are about ¼ or less the width of thecoil of the induction tool.

[0053] The seaming tapes of this embodiment may be constructed indifferent ways. The simplest and most cost effective manner involves theapplication of the susceptor material over the whole of the surface ofthe base layer followed by a scoring of the susceptor layer so as toelectrically isolate the scored edge strips 13 from the rest of thesusceptor 14. Alternatively, the susceptor layer 12 comprises asusceptor element and two edge strips 13 of a damming material that areindependently laid on the base layer 11, preferably with a gap betweenthe edge strips and the susceptor element. Depending upon the selectionof the material from which the base layer is made, it may be necessaryto apply an adhesive to the underside of the susceptor material and/ordamming material in order to ensure a strong bond. Additionally,although not necessary, in constructing the tape according to thisembodiment, the base layer may be wider than the susceptor layer so asto leave an edge, much like traditional seaming tapes. However, thisadds costs and increased difficulty in manufacture due to the use ofmore material, i.e., a wider base tape, and the need for precision inensuring that the susceptor layer elements are properly centered on thetape. Such precision may be difficult in high-speed continuousmanufacturing operations.

[0054] The foregoing discussion just as readily applies to themanufacture and construction of those tapes that are activated byresistance heating as well: the only difference being to ensure that theelectro-responsive material is a suitable conductor for the specificapplication. As with the induction tapes, the key is to isolate a narrowregion along each edge that is not electrically activated. As with thesusceptor, it may be a matter of scoring (cutting) the edge of a wideconductive foil or the laying of independent damming materials. If aseries of inductive elements were laid side-by-side along the length ofthe tape, one could achieve the “dead zone” effect merely by notattaching the current lead to those conductive elements near the edgesof the tape.

[0055] The foregoing tapes may be activated by resistance heating,wherein a lead is attached to each end of the tape or, where the tapehas two or more conductive elements with a conductive bridge at one end,to each conductive element at the other end and a current passed throughthe conductive element to heat the adhesive, or by induction. In thelatter, essentially any type of induction tool may be used to induceactivation of the adhesive. Suitable induction tools are described in,for example, Riess et. al. U.S. Pat. No. 6,509,555 and Sakai et. al. JP1200937. Alternatively, and preferably, the tapes according to thisembodiment are induced using induction tools having a “double racetrack”coil, i.e, two induction coils, preferably elliptical in shape and ofthe pancake style, in a side-by-side relationship, each coil, inoperation, on opposing sides of the centerline of the seaming tape. FIG.4 shows the footprint of a double racetrack induction coil 20 having twoelliptical coil elements 21 with opposite current flows 29 separated bygap 22 on opposing sides of the central axis 23 of the tool. Thefunctional length 25 of the coil 21 corresponds to that length ofsusceptor able to be heated to the appropriate temperature by the coil.As discussed further below, the double racetrack coil not only providesexcellent heating at the edges of the susceptor element, but alsoprovides marked heating at the centerline of the tape.

[0056] Regardless of what tool is chosen, the seam is formed bycentering the improved carpet seaming tape below the carpet seam,placing the opposing edges of the carpet in butt end relationship withthe seam overlying the centerline of the underlying seaming tape,placing the induction tool over the seam with the central axis of thetool generally overlying the seam, and, thus, the centerline of thetape, activating the tool for a sufficient period of time in order tomelt the adhesive on the tape, moving the induction tool forward adistance equal to or less than the functional length of the inductioncoil to heat the next contiguous section of tape while concurrentlypressing the trailing carpet edges into the molten adhesive. Leakage orsqueeze out of adhesive is prevented as a result of the “dead” zones.Specifically, in those seaming tape constructions where the adhesiveoverlies the edge strips, any heat generated in the edge strips and/orconducted through the adhesive from the susceptor element isinsufficient to melt the adhesive. Thus, the adhesive overlying the edgestrip acts as a dam. Where the adhesive does not overlie the dead zoneor only in a minor way, molten adhesive over the susceptor element mayflow towards the edges but is quickly cooled and its flow stopped as theheat from the molten adhesive is absorbed by the heat sink.

[0057] In addition, this concept allows for the mass production ofseaming tapes wherein the foundation of the seaming tape is firstproduced in wide stock rolls. These stock rolls are then cut to thedesired width of the final tape and scored to create the appropriate“dead” zones. For example, a single stock roll of the tape foundationcould be formed that is several feet wide and is subsequently cut intoindividual 3 inch or 4 inch wide tapes. In manufacturing the stockrolls, each layer of material making up the tape foundation issequentially laid, one upon the other, across the full width of thestock roll. Thereafter, the remaining layers of the tape aresequentially added to cut stock rolls to form the final tapeconstruction. Alternatively, if the stock roll is to be used tomanufacture a single width tape, it is possible to complete the buildupof the final tape, before cutting the rolls from the foundation tape, byscoring the bulk roll of the tape foundation and thereafter continuingwith the build-up. In this embodiment, each layer, including theadhesive, would run from one edge of the tape to the other. Without the“dead” zones, these tapes would readily ooze adhesive from the edge ofthe tape. Thus, tapes according to this aspect of the invention providea number of manufacturing and materials related cost efficiencies aswell as addressing the problems of adhesive leakage and squeeze-out.

[0058] In a second aspect of the present invention the susceptor elementor layer is scored (cut through) along its central axis, not to preventmelting of the adhesive, but to enhance melting of adhesive in the areaproximate to the scoring. FIG. 5 shows a cross section of the foundation30 of a seaming tape made in accordance with this embodiment of thepresent invention wherein a susceptor layer 33 is centrally disposed ona base layer 32 whose width is greater than that of the susceptor layer,leaving exposed edges 35 of the base layer to catch any leakage orsqueeze out of adhesive. Alternatively, the width of the base layer andthe susceptor layer may be the same, especially if the overall width ofthe susceptor is significantly larger than that of the coil. Critical tothis embodiment is the scoring of the susceptor layer along itscenterline, forming slit 34 along the length of the tape. The scoringisolates each portion of the severed susceptor element from the other.As shown in FIG. 6, the seaming tape is completed by the subsequentaddition of one or more adhesive layers 36 and, optionally, areinforcing layer 37, which may be directly adhered to the susceptorlayer or applied to an intervening adhesive layer 36 a. The top oruppermost layer of the construction is an adhesive layer. Alternatively,rather than applying a single susceptor layer and scoring it, one canachieve the same effect by placing two strips of susceptor element in aparallel, co-planar relationship, separated by a minor gap, sufficientjust to electrically isolate one from the other.

[0059] In a preferred embodiment of this aspect of the invention, theadhesive on the uppermost surface of the seaming tape will be thicker inthat region overlaying the centerline of the tape, essentiallycorresponding to the desired seam bond or bond width. Generally, thewidth of this region of thicker adhesive overlying the centerline of thetape will be about 3 inches or less, but preferably no less than about ¼inch in width. However, narrower regions of 2 inches or less, butpreferably no less than ½ inch, are more common. The thickness of theadhesive in this region will be from about 40 to 200 mils, preferablyfrom about 50 to 150 mils. This will generally correspond to a thicknessof one and one-half to five, preferably two to three, times the averagethickness of the adhesive across the width of the tape in those tapeswhere adhesive covers all or substantially all of the susceptor surfacearea. Whatever the exact thickness may be, the purpose of this centralridge or strip of adhesive is to provide excess adhesive that flows intothe seam providing a strong bond between the opposing butt ends of thecarpet so as to avoid peaking when the carpet is stretched. Oftentimes,with thin films of adhesive over the whole of the tape or, especially inthe central region, there is insufficient adhesive to flow into the seamand bond the butt ends together. Consequently, when the carpeting isstretched, the seam, or at least the upper portion of the seam may open,causing peaking of the carpet seam. The excess or thicker regions ofadhesive are not necessarily limited to the central area of the tape.Such thicker regions may also be employed at the outer edges of thesusceptor elements as well as in the central region to provide betteroverall bond strength across the whole of the seam area, including boththe centerline bond area and the edge region.

[0060] It is also contemplated that this embodiment of the invention mayintegrate the “dead” zone concept of the prior embodiment. In thisrespect, the susceptor layer may be formed by scoring a susceptorelement three times: once at the centerline and once at the appropriatedistance in from each outer edge of the tape so as to form the edgestrips, as taught previously. Alternatively, the tape may be made bylaying each edge strip and each susceptor element strip independently orby scoring the centerline of the susceptor element and laying the edgestrips independently. Furthermore, where the tape construction employssuch “dead” zones, it is not necessary to use a base layer that is widerthan the susceptor layer to prevent adhesive from leaking out andbonding the carpet to the underlying substrate.

[0061] This aspect of the invention is especially beneficial as itenables the applicator to use traditional induction tools having asingle coil or multiple, in-line coils, of the type described in Reisset. al. and Sakai et. al., respectively. Suitable coils may be ofdifferent shapes, e.g., square, round, oval, elliptical; but in anyevent must be properly sized so that they produce a heating pattern thatis within the desired bond band. Coils of large diameter or width incomparison to the width of the susceptor element in the tapes willresult in excessive heating at the edge of the susceptor and, possibly,subsequent scorching and/or degradation of the adhesive, tape, carpetand/or pad. Generally speaking, the width or diameter of the coil willbe such that the width of the susceptor will be from about 1.0 to 1.5times the width of the coil, preferably from greater than 1 to 1.3 timesthe width of the coil and most preferably about 1.1 to 1.2 times thewidth of the coil. Here, the width of the susceptor is the combinedwidth of the individual/scored susceptor elements.

[0062] This aspect of the present invention allows the construction ofseams without concerns that gaps or weak areas in the bond at the seamwill appear, particularly where one employs an excess of adhesive in thecenterline region. Specifically, the present invention allows for theuse of tools that previously provided little or barely sufficient heatat the centerline of conventional, non-scored induction tapes or didproduce sufficient heat but also produced gaps along the bondline wherethe “center” of the wound coil was located during activation. Such toolsin combination with the inventive tapes provide more than sufficientheat in the centerline region to melt not only a traditional thicknessof hot melt adhesive but an excess of the adhesive as well. In essence,the centerline benefits from the heat of the two opposing edges of thescored susceptor element as compared to the heat of the single edge atthe outer edge of the susceptor. Thus, the combination of these newcarpet seaming tapes and the traditional induction tools provides a newand useful method of carpet seaming as well as a synergistic carpetseaming system.

[0063] The method of use of the tapes and tools of this aspect of theinvention are the same as mentioned above for the tapes having the“dead” zones. Specifically, the tape is placed under the carpet with thecenterline of the tape corresponding to the seam. The carpet edges areplaced together, the tool aligned with the seam and activated for asufficient period of time to melt the adhesive. Then, the tool isadvanced to the next activation site and the trailing seam pressed toforce the backing of the carpet into the hot melt adhesive. This processis repeated until the tape seam is completed.

[0064] In a third aspect of the present invention, there is provided animproved induction carpet seaming method wherein tapes of the typedescribed above as well as conventional induction activatable carpetseaming tapes may be used in combination with an induction tool having a“double racetrack” coil for providing carpet seams with strong bondseven at the centerline of the tape. This aspect of the present inventionalso relates to novel tapes and tools specifically designed for use inthe aforementioned method.

[0065] As discussed earlier, FIG. 4 shows the footprint of a doubleracetrack coil with its opposite current paths 29. For purposes ofexaggerating the opposing flow, the arrows are shown outside of the coilelements 21, when in fact the flow is within the coil elements of thecoil 20. Although the particular embodiment shown is of dual ellipticalcoil elements 21, the coil elements could just as well be of a differentshape, e.g., circular, square or rectangular; however, shape may affectthe efficacy of the tool, particularly insofar as the shape affects thefunctional length of the coil, and thus tool. In particular, it has beenfound that the geometry of the coils affects the heating characteristicsfor a susceptor of a given width and thickness. The chief variables ofthe coil geometry are the wire type, total length of wire, windingpattern, and separation between the two lobes of the coil, all of whichdetermine the centerline activation width 28 and the overall coil width27 as well as the functional length 25 of the tool. The coil length isselected to balance power transfer, activation cycle time, and desiredseaming rate. For example, a typical 120V AC powered tool can activateabout 1 inch/second of seam tape that is coated with a low melttemperature, hot melt adhesive that is approximately 0.8 mm thick. Acoil having a functional length of 8 inches would require about 8seconds to activate the 8 inches of seam it covers. The cycle time isthen about 10 seconds (allowing 2 seconds to move the tool) giving aseaming rate up to 48 inches per minute—a rate very competitive with hotiron seaming which is assumed to be approximately 3 feet per minute.

[0066] The coil separation 22 must also be optimized to maximize thewidth of the heating band or, alternatively, minimize the total coilwidth while maintaining acceptable heating distribution in the heatedband, i.e., the area corresponding to the centerline bond band. Thepower distribution as a function of separation between the coils isillustrated in FIG. 7. For clarity, the coil winding position, relativeto the centerline axis of the tool, is also shown for each designatedseparation of the coils (71, 72, 73, 74). This corresponds to the crosssection of one of the two individual coil elements in FIG. 4 taken alongline 4 a-4 a, with the gap 22 being equal to the specified separationshown in FIG. 7. In FIG. 7, the Power Density axis of the graphcorresponds to the centerline of the coil 23 (of FIG. 4). Combining amirror image of the plot at the power density axis would provide arepresentation of the power density across the full width of thesusceptor.

[0067] As seen in FIG. 7, when the coil separation is zero 71, theheating bandwidth is minimum and the power distribution, and thereforethe temperature, is greatest at the centerline of the coils. At constantpower and energy, we find that as the coil separation is increased theuseful heated zone, i.e., that area corresponding essentially to thecenterline activation width 28, widens and the magnitude of the heatingmaximum located at the centerline falls. This manifestation is shown bythe plots 72, 73 and 74 for coil separations of 10 mm, 20 mm and 30 mm,respectively. Eventually, the separation grows too large such thatheating at the centerline falls to an unacceptably low value, especiallyfor an adhesive of a given type and thickness.

[0068] Notwithstanding the foregoing, as discussed below, while coilseparations (also referred to herein as “gaps” or “coil spacing”) of thewidths mentioned above may be preferred for instances where, in use, thetool or coil is properly aligned over the centerline of the tape, suchis not always possible. Consequently, although there is a trade off inthe power density in the centerline region with wider gaps, such widergaps also provide an overall wider activation width, as seen in FIG. 7,so that if misalignment occurs, there is still a sufficiently wide seambond band formed. Of course the gap must not be so great as to result intoo little power and poor heating. In this instance, wider coil elementscombined with wide, but not excessively wide gaps, can accommodate powerneeds together with addressing the activation width.

[0069] As a consequence of their experimentation, Applicants havedesigned an induction tool that is especially beneficial for carpetseaming and like seaming applications. As shown in FIG. 4, tools inaccordance with this aspect of the present invention have a coil spacingor gap 22 of between 5 and 30 mm, preferably between 10 and 20 mm; acenterline activation width 28, i.e., that distance from the inside edgeof one coil loop to the inside edge of the opposing coil loop, of atleast about 0.75 inch, preferably at least about 1.0 inch, but generallyless than 3 inches, most preferably about 2 inches, and an overall coilwidth 27 that is less than the width of the susceptor of the tape to beactivated and will most likely be of no more than about six inches,preferably no more than about four and one-half inches. In following,the element width 26 of the coil elements will be from about 0.25 toabout 0.75 inch, preferably about 0.5 inch. The functional length 25 ofthe coil, i.e., the straight edge portion of the coil, can vary and ismore a function of the economics and power output of the tool as well asthe desired speed of the seaming process. Generally speaking, thefunctional length is between about 2 to 12 inches, preferably from about4 to 10 inches. Longer functional lengths, though possible, make thetool cost ineffective and more difficult to use, particularly from ahand-held perspective. Shorter functional lengths make the toolsdifficult to use in that so many more individual advancement andactivation steps will be required to bond a seam of a given length.

[0070] Seaming tapes to be used with the foregoing double racetrackcoils will have a susceptor width that is at least the same as,preferably greater than the overall coil width 27, preferably from about1.05 to 2.5 times, more preferably 1.1 to 1.5 times, the width of thecoil. Reference here to susceptor width includes the full width(combined width) of the active susceptors in the case where a slitsusceptor is used, but excludes those portions of a susceptor that havebeen isolated to create “dead” zones or that are so narrow as not to berecognized by the induction tool. Wider susceptors could be used, but,except as noted below with respect to addressing concerns of inductiontool misalignment, there is no performance benefit and the costsassociated with the susceptors make them less desirable. If thesusceptor width is smaller than the overall coil width then very strongedge heating occurs in the susceptor and edge burning or overheatingwill occur before or by the time that the center region is sufficientlyheated to form a suitable carpet seam. This overheating results indamage to the secondary carpet backing, reducing strength, which maylead to carpet seam failure during stretching. Furthermore, there comesa point where the susceptor width is so small that the induction toolfails to recognize the susceptor altogether, much as noted above withthe “dead zones. Thus, where a slit susceptor is used to activate theadhesive, the individual susceptor elements should be at least about ½,preferably at least about ⅔, the width of the coil.

[0071]FIG. 8 illustrates the calculated results of a series of finiteelement analyses using the analysis program MEGA from the University ofBath, in the United Kingdom for tapes having susceptors of differentwidths when activated by a double racetrack induction coil having anoverall width (denoted by number 27, in FIG. 4) of 78 mm. Plots 81, 82and 83 correspond to susceptor widths of 80 mm, 90 mm and approximately178 mm, respectively. Plot 81, which illustrates the normalized powerdensity profile of a susceptor that is approximately 1.026 times thewidth of the coil, shows a high edge effect heating, nearly twice asmuch power density is delivered to the edge as to the centerline. Plot82, which illustrates the normalized power density profile of asusceptor that is approximately 1.154 times the width of the coil, showsa relatively even heating between the centerline and the edge. Suchheating characteristic is especially desirable. Finally, Plot 83, whichillustrates the normalized power density profile of a susceptor that isapproximately 2.24 times the width of the coil, shows good centerlineheating with little edge effect heating. Such a power density profile isdesirable, as noted above, where there is only a desire to bond at thecenterline and/or no adhesive is found in the edge region of thesusceptor. Depending upon the thickness and transition temperature ofthe adhesive, as well as the duration of activation of the tool, it isclear that susceptor width can play a major role in the efficacy of aseam.

[0072] Generally speaking, as noted above, the desired power densitycharacteristic is where the power density at the centerline isequivalent to or nearly equivalent to the power density at the susceptoredge, especially where the adhesive thickness is relatively constantacross the width of the tape or at least in the centerline and edgeregions. Of course, some variation in the power density is not ofconcern and would be desired if the higher power density corresponded toa thicker region of adhesive. Still, since heat transfer from thesusceptor to the adhesive and, perhaps more importantly, through theadhesive itself, is a limiting factor, there is the opportunity forexcessive heat build up in regions of the susceptor having higher powerdensity. Thus, very high power density is not necessarily desirable asthe heat may not transfer quick enough to avoid scorching in theaffected region. Additionally, since the thickness of the susceptor alsoaffects energy absorption, thus power density buildup, it is alsopossible to vary the thickness of the susceptor in given regions tolessen the disparity in power density. Increasing susceptor thicknesswill decrease power dissipation (at a fixed coil excitation current).This, however, introduces other issues, including cost factors that maymake this a less desirable alternative. In any event, given the sharpincrease in power density at the edge between Plots 81 and 82, it isclear that while susceptors that have a width the same as the coil maybe suitable, widths smaller than the coil will lead to unacceptable edgeheating and failure.

[0073] The seaming tapes according to the preferred embodiment of thisaspect of the present invention must have adhesive in both thecenterline region and in the area overlying the edges of the susceptors,unless the susceptor is much wider, e.g., at least about 1.25,preferably at least about 1.5, times wider, than the coil width. This isbecause the adhesive overlying the edges of the susceptors acts as aheat sink, absorbing heat generated in the edge region. Generallyspeaking, even if the power density in the edge region is not sufficientto cause scorching, it is preferable to have the adhesive present at theedge region to provide an additional bond site for the tape. It mayenhance the strength or appearance of the seam, e.g., there are some inthe art who believe the creation of a bond of good strength removed fromthe main bond or seam area will help reduce some of the stresses on theprimary seam and help alleviate peaking.

[0074] In a preferred embodiment, there are provided novel inductionactivatable seaming tapes comprising a base layer having a width of atleast four, preferably at least 4.5 inches; a susceptor layer whereinthe activatable susceptor is at least 3 and preferably at least 3.5inches wide, a reinforcing layer, and at least one adhesive layerwherein the adhesive is present in the centerline region and comprisesan adhesive strip or series of closely spaced, parallel beads in aregion that is at least 1.5, preferably about 2 inches wide. Preferably,the tape will have adhesive in the ¼ to ½ inch section of the tapedirectly overlaying the edge of the activate susceptor. In a morepreferred embodiment, the adhesive at the centerline and edges will beof sufficient thickness to allow the adhesive to work into the carpetbacking and seam area. Though seaming tapes of less than four incheswith an aluminum foil layer are commercially available for use in thehot iron seaming method where the foil provides a heat reflectivesurface, such tapes are too narrow to provide a sufficient bond band atthe centerline without overheating the edges of the tapes. Applicantshave found that by using wider tapes, they can create a tool or use atool whose coil width, especially its centerline activation width, issufficient to generate a suitably wide bond band area.

[0075] The method of forming the seams in accordance with this thirdaspect of the present invention is the same as set forth above for theother aspects. Activation times, energy levels, frequency, etc., is alla mater of choice and readily ascertainable by those skilled in the art,taking into consideration the factors mentioned in this disclosure. In apreferred aspect of the present invention, the induction tool will be asmart tool, capable of detecting energy consumption or draw by thesusceptor and adjusting the output accordingly to ensure proper heatingwithout over heating.

[0076] The foregoing discussion concerning the various aspects andembodiments of the present invention presumes, for the most part, thatthe tool is properly aligned with the centerline of the tape duringactivation of the tape, i.e., that central axis of the induction tool orcoil, in the case of the double racetrack coil, is centered over thecenterline of the tape. This is important inasmuch as misalignment ofthe tool relative to the centerline of the tape will adversely affectthe optimal performance of the activation and, thus, the seam to beformed. To avoid such concerns, one may use an apparatus or tool whichaligns the induction tool directly over the seam. Such tools aredisclosed in U.S. Provisional Patent Application Serial No. 60/443,403,filed Jan. 29, 2003, of Green et. al. Additionally, one could adaptalignment tools used for hot iron seaming methods to be used forinduction tools as well, see e.g., Anderson, U.S. Pat. No. 4,584,040.

[0077] Alternatively, one can modify the widths of the tapes andsusceptors to account for misalignment. In this respect, for each ¼ inchthat the tool is aligned off of the centerline of the tape, the width ofthe susceptor will need to be an additional ½ inch wider overall. Thisis because the heating pattern for a given tool will shift equally withthe misalignment, i.e., if the tool is misaligned by ⅓ inch, then theheating pattern is likewise misaligned by the same ⅓ inch. The need toincrease the susceptor width to accommodate misalignment is particularlyimportant, if not critical in the absence of an alignment tool orextreme skill, where the width of the susceptor is less than 1.1 timesthe width of the coil, perhaps even less than 1.2 times the width of thecoil, depending upon the skill of the operator as well as the absolutedimensions of the tool and susceptor. For example, if the tool were of 4inch width and the susceptor 4.8 inches (1.2 times the width of thecoil), a misalignment of ¼ inch may not be an issue whereas a ½ inchmisalignment may. Thus, in commercializing a tape for use with a giventool, one may want to accommodate a predetermined level of misalignment,by incorporating additional width into the susceptor to act as atolerance for the misalignment. Again, by way of illustration, if theoptimum susceptor width for a given tool, assuming exact alignment, is1.1 times the width of the coil, but the likely skill is such thattypically one could expect up to ½ inch misalignment, then the optimumsusceptor width, for commercial purposes, will be 1.1 times the width ofthe coil plus 1 inch. Thus, the ranges of acceptable widths recitedabove for the susceptors would be adjusted accordingly, and suchenhanced width tapes, systems and methods are and are intended to beencompassed by and embraced by the teaching of this patent and itsclaims. In these instances, wider gaps between the coils of the doubleracetrack coil and/or wider coil elements resulting in wider overallactivation widths (28 in FIG. 4) are desirable to help offset concernsof misalignment.

[0078] Furthermore, while the foregoing discussion has focused on aproper alignment of the axis of the induction tool and coil with thecenterline of the tape, it is also possible to bond and properlyactivate by having the axis of the induction tool perpendicular to theaxis of the tape, particularly with tools whose coils are elongated,i.e., the length of the coils are considerably larger than their widths.This method of bonding is especially applicable and desirable foreffecting bonding of the ends of the tapes. Thus, in one aspect of theseaming methods described above, the first activation may be onetransverse or perpendicular to the tape to form the initial bond at oneend of the tape followed by successive activations with the axis of thetool and the centerline being parallel until the tool reaches theopposite end of the tape where, once again, the tool is turn transverseto the tape to effect the last bond at that end of the tape. When usingthe induction tool in the transverse mode, adjustments must be maderelative to the power and energy transfer to the tape to avoid excessiveheating at the susceptor edge.

[0079] As another feature of the present invention, those skilled in theart would readily recognize that the tapes described herein can bemodified to make the same two-sided for overlap seam bonding and forbonding the rolled good to an underlying substrate. In this respect, twotapes may be bonded back to back or one may build up the tape on bothsides of the base layer.

[0080] Furthermore, while the methods described herein speak more oftenof a sequential activation and bonding, the seams of the presentinvention may also be made by a continuous seaming method where the toolis continuously or very rapidly activated or fired as the tool is movedalong the seam at a constant rate.

[0081] Finally, again, while the invention has been described mostprominently in terms of carpet seaming, it is clear that the same can beused or modified for use with any number of rolled goods and the like.Additionally, it is easily seen why the tapes, tools and seaming systemscombining the tape and the tool as taught herein provide numerousbenefits over existing technologies for seaming, particularly carpetseaming. It is also evident that these tapes, tools and systems areespecially beneficial for making repairs to rolled goods, whether at theseam or in the body of the roll goods. For example, should a burn occurin a carpet, the section can easily be excised and replaced with anothersection of carpet. This is so for even very small sections of carpet tobe replaced.

[0082] The following examples and comparative examples are provided tofurther illustrate the invention. These examples are-not meant to limitthe broad teaching and scope of the invention.

[0083] Unless otherwise indicated, the induction tool used in thefollowing examples was of the type described in Reiss et. al. (U.S. Pat.No. 6,509,555) with the exception that the coil element of the tool wasreplaced with a double racetrack coil (See FIG. 4) wherein each coilelement (21) had a functional length (25) of approximately 8 inches, anelement width (26) of approximately ½ inch, with a coil gap (22) ofapproximately ½ inch and a total width (27) of about 3 inches. Inpreparing the seam, unless otherwise indicated, the axis of the tool(23) was aligned with the centerline of the tape and the tool activateda total of 9 times to deliver the energy specified in each example andto form a bond of approximately 8 inches in length corresponding to theactivation length of the tool.

EXAMPLE 1 3½ Inch Tape with Inactive Areas to Prevent Squeeze Out

[0084] Two seaming tapes were prepared as follows. A 3½ inch wide,0.000285 inch thick aluminum foil was laminated to a 3½ inch wide basesheet that is formed of unbleached, 30# Kraft paper. A 0.007 inch thicklayer of adhesive (RHM494 available from Western Adhesives of KansasCity, Mo.) was applied to the surface of the foil using a heated iron. A3 inches wide layer of woven cotton and fiberglass mesh was placed ontop of the adhesive, centered and bonded to it using a warm iron.Another 0.007 inch thick layer of adhesive was applied to and bonded tothe top surface of the fabric mesh using a heated iron. Two layers of ½inch wide, 0.007 inch thick adhesive strips were applied to the edges ofthe tape and attached with a warm iron. The two tapes differed only inthat on one tape, prior to the first application of adhesive, a cut wasmade through the aluminum foil, but not through the Kraft paper,approximately ¼ inch from each outer edge of the tape.

[0085] A 12 inch long piece of each tape was placed on top of a ½ inchthick carpet pad made of reclaimed polyurethane foam with the adhesiveside facing away from the pad. Two pieces of beige Softbac carpet, eachabout 24 inches in length, (available from Shaw Industries) wereoverlaid on the tape and configured so that their edges met at thecenter of the tape.

[0086] The induction tool was placed on the top surface of the carpetover the tape having the cut foil and activated 9 times successively todeliver a total of 3600J at 300W. Upon examination of the back of theseam it was evident that the adhesive had melted and flowed into thebacking of the carpet up to, but not beyond, the portion of the foilthat was scored. The induction tool was then placed on the top surfaceof the carpet over the non-scored tape and activated 7 timessuccessively to deliver a total of 2800J at 300W. Upon immediateexamination of the back of the bonded seam, it was evident that theadhesive had melted and flowed beyond the width of the tape and bondedit to the carpet pad.

[0087] This example demonstrates that scoring or cutting the foilsusceptor prevented it from heating and melting the adhesive thuspreventing squeeze-out.

EXAMPLE 2 Slit Tape with Single Pancake Coil

[0088] Two seaming tapes similar in construction to FIG. 6 were preparedas follows. A 3½ inch wide, 0.000285 inch thick aluminum foil waslaminated to a 3½ inch wide base sheet that was formed of unbleached,40# Kraft. A 0.003 inch thick layer of adhesive (HM-075 available fromSouthern Chemical Formulators, Inc. of Mobile, Ala.) was applied to thealuminum surface using a heated iron. A 3 inch wide layer of wovencotton and fiberglass mesh was placed on top of the adhesive, centeredand bonded to it using a warm iron. Another 0.003 inch thick layer ofadhesive was applied and bonded to the top surface of the fabric meshusing a heated iron. Two layers of ½ inch wide adhesive strips, 0.003inch thick, were applied to the edges of the tape and attached with awarm iron. The two tapes differed only in that on one tape, prior to thefirst application of adhesive, a cut was made through the aluminum foil,but not through the Kraft paper, along the centerline of the tape.

[0089] A 12 inch long piece of each tape was placed on top of a ½ inchthick carpet pad made of reclaimed polyurethane foam with the adhesiveside facing away from the pad. Two pieces of beige Softbac carpet, eachabout 24 inches in length, (available from Shaw Industries) wereoverlaid on the tape and configured so that their edges meet at thecenter of the tape.

[0090] A single pancake type induction coil of Litz wire was wound in anelliptical shape measuring about 9 inches long and 3 inches wide. Thecoil was then attached to an induction tool of the type described inReiss et. al. The device was set to deliver 4000J at 400W.

[0091] The induction tool was placed on the top surface of the carpetover the scored tape and activated to deliver a total of 4000J at 400W.Upon examination of front and back of the seam it was evident that theadhesive had melted and flowed into the seam and had bonded across thefull width of the tape. The induction tool was then placed on the topsurface of the carpet over the non-scored tape and activated to delivera total of 4000J at 400W. Upon immediate examination of the back of thebonded seam, it was evident that the adhesive has not melted and flowedin the center of the tape.

[0092] This shows that scoring of the susceptor along the centerlineallowed a traditional induction coil to sufficiently heat the center ofregion of the tape, thus enabling a strong bond at both the center andedge regions of the tape.

EXAMPLE 3 3½ Inch Double-Sided Tape to Seam Carpet and Bond to Floor

[0093] A double-sided tape was prepared by bonding together twosingle-sided tapes constructed as follows. A 3½ inch wide, 0.000285 inchthick aluminum foil was laminated to a 3½ inch wide base sheet that isformed of unbleached, 40# Kraft paper. The aluminum foil was then coatedwith a 0.003 inch thick layer of adhesive (HM-075 available fromSouthern Chemical Formulators, Inc. of Mobile, Ala.). Two layers of ½inch wide, 0.003 inch thick, adhesive strips were applied to the edgesof the tape and two layers of 1 inch wide, 0.003 inch thick adhesivefilm were applied to the center of the tape and attached with a warmiron. The single sided tapes were bonded to one another by applyingspray adhesive to the paper backings and pressing them together to formthe double-sided tape.

[0094] A 30 inch long piece of the double-sided tape was placed on topof a ¼ inch thick plywood board. Two pieces of beige Softbac carpet,each about 30 inches in length, (available from Shaw Industries) wereoverlaid on the tape and configured so that their edges metperpendicular to the center of the tape. The above-mentioned tool havinga double racetrack induction coil of ½ inch coil spacing and 8 inches inoverall length was placed on the top surface of the carpet over the tapeand activated to deliver 4500J at 500W. Upon immediate examination ofthe bond, it was evident that the seam had been made and the carpet wassecurely bonded to the plywood.

EXAMPLE 4 3½ Inch Double-Sided Tape to Seam Textiles

[0095] A double-sided tape was prepared as in Example 3. A 12 incheslong piece of the double-sided tape was placed between two 9 inches longcloth strips to form an overlap seam between the pieces of fabric. Theinduction tool was placed over the seam and activated to deliver 2500Jat 300W. Upon immediate examination of the bond, it was evident that theseam had been made and the fabric pieces were securely bonded to oneanother.

EXAMPLE 5 3½ Inch Single-Sided Low Profile Tape to Form Butt Carpet Seam

[0096] A 3½ inch wide, 0.000285 inch thick aluminum foil was laminatedto a 3½ inch wide base sheet that is formed of unbleached, 40# Kraftpaper. The aluminum foil was then coated with a 0.003 inch thick layerof adhesive (HM-075 available from Southern Chemical Formulators, Inc.of Mobile, Ala.). A 3 inches wide layer of woven cotton and fiberglassmesh was placed on top of the adhesive, centered and bonded to it usinga warm iron. Another 0.003 inch thick layer of HM-075 was applied to andbonded to the top surface of the fabric mesh. Two layers of ½ inch wide,0.003 inch thick adhesive strips, were applied to the edges of the tapeand two layers of 1 inch wide, 0.003 inch thick, adhesive film wereapplied to the center of the tape and attached with a warm iron.

[0097] A 12 inch long piece of this tape was placed on top of a ½ inchthick carpet pad made of reclaimed polyurethane foam with the adhesiveside facing away from the pad (toward the carpet backing). Two pieces ofbeige Softbac carpet, each about 24 inches in length, (available fromShaw Industries) were overlaid on the tape and configured so that theiredges met at the center of the tape. The induction tool was placed onthe top surface of the carpet over the tape and activated to deliver4000J at 400W (10 second activation). Upon immediate examination of thebond, it was evident that the adhesive had melted and flowed into thebacking of the carpet.

[0098] This procedure was repeated again on a larger piece of carpet andthe induction tool was used to activate the adhesive tape ahead of thecarpet installer. The installer activated the tape, slid the toolapproximately 7 inch to the next location, activated it again, and whilewaiting for the subsequent activation, briefly inspected the carpet toensure the desired seam was produced and found that the work necessaryto create the desired seam was less time-consuming than with the hotiron method. This procedure was very similar to the procedure used todaywith the added benefits described above. After the seam was complete,the adhesive was allowed to cool without examination of the bond. Thecarpet was stretched with a power stretcher and placed on tack stripsdesigned to secure carpet to flooring. The seam remained intactthroughout the operation and upon visual examination, appeared to be ofhigher quality than one produced adjacent to it using the traditionalhot iron method.

EXAMPLE 6 3½ Inch Single-Sided Tape with Excess Adhesive at Edges andCenter

[0099] A tape was prepared in accordance with Example 5 following whicha bead of adhesive (HM-049 available from Southern Chemical Formulators,Inc. of Mobile, Ala.) inch diameter was affixed to the center of thetape using an aerosol adhesive.

[0100] A 12 inch long piece of this tape was placed on top of a ½ inchthick carpet pad made of reclaimed polyurethane foam with the adhesiveside facing away from the pad. Two pieces of beige Softbac carpet, eachabout 24 inches in length, (available from Shaw Industries) wereoverlaid on the tape and configured so that their edges met at thecenter of the tape. The induction tool was placed on the top surface ofthe carpet over the tape and activated to deliver 4000J at 400W. Uponimmediate examination of the bond, it was evident that the central beadof adhesive had melted and flowed onto the edges of the carpet backing.

EXAMPLE 7 Conventional Hot Iron Tapes v. Induction Tape

[0101] In this example three commercially available 3.75 inch wide hotiron seaming tapes, each having an aluminum foil layer incorporated intoand extending the full width of the backing to reflect heat passingthrough the hot melt from the iron and thus, presumably, enhancing meltof the hot melt adhesive, and an adhesive layer that provided anadhesive free edge of about ½ wide along each edge of the tape, a 1.9375inch wide electrically activated seaming tape having a 0.002 inchconductive foil layer for resistive heating and a 4.5 inch wideinduction activatable seaming tape made in accordance with the teachingof the present invention were evaluated to assess their activation byinduction. The three commercial tapes were Bond Loc 90LTG, Roberts GT330and Seam Master Gold.

[0102] A 12 inch long piece of each tape was placed on top of a ½ inchthick carpet pad made of reclaimed polyurethane foam with the adhesiveside facing away from the pad (toward the carpet backing). Two pieces ofbeige Softbac carpet, each about 12 inches in length, (available fromShaw Industries) were overlaid on the tape and configured so that theiredges met at the center of each tape. In these series of experiments,the double racetrack induction tool had a coil separation or gap ofabout ⅝ inch and a total coil width of about 3⅝ inches. The inductiontool was placed on the top surface of the carpet over the tape andactivated to deliver 3500J at 600W.

[0103] Examination of the seams formed with the three commercial hotiron tapes showed visible signs of paper charring and damage to thecarpet, evidence of overheating in the edge region of the reflectivefoil. Without adhesive overlying the edges of the reflective foil, thereis no heat sink, other than the paper backing and carpet, to absorb theheat generated in the foil edge. The centerline area of the tape showedpoor and intermittent melting of adhesive, indicative of an incompleteseam with little or poor strength. Because of the limited width andthickness of the conductive element of the resistance tape, theinduction tool failed to recognize the tape and did not deliver anyenergy to the tape. On the other hand, the tapes made in accordance withthe teaching of the present invention showed no signs of charring oroverheating but excellent activation, thus melting of adhesive, in thecenterline region of the tape.

[0104] It should be understood that the foregoing description is onlyillustrative of the invention. Various alternatives and modificationscan be devised by those skilled in the art without departing from theinvention. Accordingly, the present invention is intended to embrace allsuch alternatives, modifications and variances falling within the scopeof the appended claims.

We claim:
 1. An induction activatable tape comprising a base layer, a susceptor overlaying all or a substantial portion of the base layer and capable of generating heat upon exposure to electromagnetic energy, said susceptor having a linear gap along the axis of the tape at or proximate to the centerline of the tape and an adhesive layer in heat transfer relationship with said susceptor and overlying all or a portion of the susceptor, but in any event overlies the susceptor at the point of the linear gap.
 2. The induction activatable tape of claim 1 wherein said adhesive layer overlies the whole of the susceptor and has a thickness in the region overlying the centerline of the tape that is at least one and one-half times the average thickness of the adhesive across the full width of the tape.
 3. A bonding system comprising: (a) induction activatable tape comprising a base layer, a susceptor overlaying all or a substantial portion of the base layer and capable of generating heat upon exposure to electromagnetic energy, said susceptor having a linear gap along the axis of the tape at or proximate to the centerline of the tape and an adhesive layer in heat transfer relationship with said susceptor and overlying all or a portion of the susceptor, but in any event overlies the susceptor at the point of the linear gap; and (b) an induction tool whose axis, in operation, parallels the centerline of the seaming tape comprising an induction coil whose width is the same as or less than the width of the susceptor.
 4. The bonding system of claim 3 wherein said adhesive layer overlies the whole of the susceptor and has a thickness in the region overlying the centerline of the tape that is at least one and one-half times the average thickness of the adhesive across the full width of the tape
 5. The bonding system of claim 3 wherein the width of the susceptor is from 1.05 to 2.5 times the width of the induction coil.
 6. A bonding tape comprising a base layer, an electro-responsive material centered on the base layer and extending in both directions from the centerline of the tape to an edge that is from ½ to ¼ inch from the edge of the base layer and two edge strips of a damming material, each edge strip overlying the whole or a portion of the base layer in the two regions between the edges of the tape and the edges of the electro-response material, and an adhesive layer in heat transfer relationship with said electro-response material, said adhesive layer overlying all or a portion of the electro-response material.
 7. The bonding tape of claim 6 wherein the electro-response material is selected from an induction activatable susceptor and a conductive resistance element.
 8. The bonding tape of claim 6 wherein the composition of the electro-response material and the damming material are the same and the edge strips are formed by scoring the electro-response material so as to electrically isolate edge portions of the electro-response material from the center portion, thereby creating heat sink strips.
 9. The bonding tape of claim 6 wherein the adhesive overlies all or a portion of the damming material as well.
 10. The bonding tape of claim 6 wherein the electro-response material comprises two individual electro-response elements separated by a gap running along its axis at or proximate to the centerline of the tape.
 11. The bonding tape of claim 6 wherein the tape is induction activated and the electromagnetic response material is a susceptor.
 12. The bonding tape of claim 6 wherein the tape is electrically activated and the electro-response material is an electrical conductor that generates heat by resistance.
 13. A bonding system comprising: (a) a susceptor centered on the base layer and extending in both directions from the centerline of the tape to an edge that is from ½ to ¼ inch from the edge of the base layer and two edge strips of a damming material, each edge strip overlying the whole or a portion of the base layer in the two regions between the edges of the tape and the edges of the susceptor, and an adhesive layer in heat transfer relationship with said susceptor, said adhesive layer overlying all or a portion of the susceptor; and (b) an induction tool whose axis, in operation, parallels the centerline of the seaming tape comprising an induction coil whose width is the same as or less than the width of the susceptor.
 14. The bonding system of claim 13 wherein the susceptor comprises two individual susceptor elements separated by a gap running along its axis at or proximate to the centerline of the tape.
 15. A bonding system comprising: (a) an induction activatable seaming tape comprising a base layer, a susceptor overlaying all or a substantial portion of the base layer and capable of generating heat upon exposure to electromagnetic energy and an adhesive layer in heat transfer relationship with said susceptor, said adhesive layer overlying all or a portion of the susceptor; and (b) an induction tool wherein the coil is a double racetrack coil.
 16. The bonding system of claim 15 wherein the coil of the induction tool has a coil spacing of from about 5 to 30 mm and coils loop elements of about 0.25 inch to about 0.75 inch wide and wherein the susceptor is from about 1.05 to about 2.5 times the overall width of the coil.
 17. The bonding system of claim 15 wherein the susceptor is at least about 4 inches wide.
 18. The bonding system of claim 15 wherein the adhesive is thicker in the centerline region of the tape or in both the centerline region and the region of the tape overlying the edges of the susceptors.
 19. An improved induction tool wherein the improvement is a double racetrack coil element having a coil spacing of at least about 5 mm and coils loop elements of at least bout 0.25 inch.
 20. The improved induction tool of claim 19 wherein the coil spacing is from about 5 to about 40 mm and the coil elements are from about 0.25 to about 0.75 inches wide.
 21. The improved induction tool of claim 19 wherein the coil elements are made of Litz wire.
 22. The improved induction tool of claim 19 wherein the overall width of the double racetrack induction coil is from about three to about six inches wide.
 23. An induction activatable bonding tape comprising a base layer, a susceptor overlaying all or a substantial portion of the base layer and capable of generating heat upon exposure to electromagnetic energy, said susceptor being at least four inches wide, and an adhesive layer in heat transfer relationship with said susceptor and overlying all or a portion of the susceptor.
 24. An improved induction seaming method for activating an induction activatable seaming tape having a susceptor with an induction tool wherein the improvement comprises the step of turning the induction tool transverse to the tape during the seaming of the end portions of the tape in order to better activate the ends of the seaming tape.
 25. The induction seaming method of claim 24 wherein the induction tool has a coil element whose length is longer that the width of the susceptor and whose width is narrower than the susceptor 